Products such as mobile telephones, digital AV equipment, IC cards, and the like have been improved to have more sophisticated functions. This gives rise to an increase in a demand that semiconductor silicon chips (hereinafter referred to as chips) provided in the products are downsized and thinned so that silicon can be provided with higher density in a package. For example, for an integrated circuit in which a plurality of chips are provided in one package, such as a CSP (chip size package) or an MCP (multi-chip package), there is a demand that the chips are thinned. In order to provide the chips with higher density in the package, it is necessary to thin the chips to a thickness in a range of 25 μm to 150 μm.
By a grinding process, semiconductor wafers (hereinafter referred to as wafers) which serve as bases for the respective chips are thinned. This, however, weakens strengths of the wafers. With the strengths of the wafers being weakened, it is easy that cracks or curls are formed in the wafer. Further, the wafers thus weakened in strength by the thinning are difficult to transfer with an automatic transporting process and need to be carried manually. As understood from this, handling of the wafers is troublesome.
As a countermeasure, a wafer handling system is developed which adds strengths to the wafers. According to the wafer handling system, a plate called a support plate, which is made from glass, rigid glass, or the like, is attached to the wafers to be thinned so that the wafers are protected from being cracked or curled. Because the strengths of the wafers can be thus secured by the wafer handling system, it is possible to automatically transport the wafers after the thinning process.
In the wafer handling system, the wafers and the support plate are attached to each other by use of an adhesive tape, a thermoplastic resin, an adhesive agent, or the like. Then, the wafers to which the support plate is attached are thinned. After this, the support plate is removed from a substrate before the wafers are diced. Specifically, in a case where the wafer and the support plate are attached to each other with the use of the adhesive agent, the wafers are removed from the support plate by dissolving the adhesive agent.
As the adhesive agent, hydrocarbon-based adhesive agents have been developed in recent years (see Patent Literatures 1 and 2).